Semiconductor and large area substrate processing systems generally include a process chamber having a pedestal for supporting a substrate, such as a semiconductor substrate, within the chamber proximate a processing zone. The chamber forms a vacuum enclosure defining, in part, the processing zone for performing certain processes upon the substrate. These processes may include deposition processes, such as chemical vapor deposition (CVD), to deposit a material on the substrate or an etch reaction to remove material from the substrate.
Most CVD processes require multiple process gases to be combined and form a gaseous mixture in a mixing device. The gaseous mixture may be delivered directly to the processing zone above the substrate within the CVD chamber, or may travel through one or more conduits and channels within a showerhead or gas distribution assembly near an upper portion of the CVD chamber. The showerhead or gas distribution assembly generally includes a face plate having a plurality of holes or channels such that the gaseous mixture is evenly introduced into the processing zone and uniformly distributed across the whole surface of the substrate.
Heating of the process gases as they enter into the processing zone may be necessary in controlling the reactivity of the gases and thus the property of the thin film deposited on the surface of the substrate. As the gaseous mixture is infused with thermal energy, a thermal decomposition reaction occurs between the process gases, resulting in a chemical vapor deposition reaction on the surface of the substrate. In addition, cooling of the process gases can be helpful in controlling unwanted reactions prior to release into the processing zone as the process gases refrain from reacting until they come into contact with a heated substrate.
In general, one or more fluids and process gases are heated in a thermal CVD process and/or energized into plasma in a plasma enhanced chemical vapor deposition (PECVD) process prior to being delivered above the substrate. A plasma enhanced deposition process or a very high thermal deposition temperature (e.g., more than 800° C. or higher than 1100° C.) is generally used to deposit thin film on the substrate and helps to prevent and remove impurities (e.g., amorphous carbon contaminants) in the deposited thin films. In addition, purging or cleaning with a heated gas may help remove contaminants from a processing chamber.
However, damage to existing structures on the surface of a patterned substrate arise very often when plasma or high deposition temperature is used. In addition, PECVD processes suffer from various undesirable limitations, such as: low process gas utilization (for example, about 3% to 20%); poor uniformity of the thin films deposited on the substrate surface; introduction of defects induced by plasma in the deposited films or in the substrates themselves; static deposition due to electrical grounding requirement; difficulty in scaling-up because of RF requirements; high system cost; low deposition rate (for example, approximately 0.5 nm/s for silicon); and the need to clean deposition chambers using NF3 (a greenhouse gas). Thus, there is a need for an improved CVD processing tool to be used at a lower processing temperature and without the use of plasma.
Hot-wire chemical vapor deposition (HWCVD) processes are potentially suitable for silicon thin film deposition. In a HWCVD process, thermal decomposition of the process gases is facilitated by having one or more wires, or filaments supported in a CVD process chamber such that the need for forming plasma or the need to use high processing temperatures as seen in a thermal CVD process is eliminated. The wires or filaments inside a HWCVD process chamber are generally heated to a desired temperature by passing electrical current through the filaments and thus causing the generation of radicals from process gases within the HWCVD process chamber.
However, there are no robust manufacturing tools suitable to realize the full potential of a HWCVD thin film deposition process. Substrate processing by a HWCVD process was not widely used than conventional thermal or plasma enhanced CVD process. The problems are associated with reaction of some excited process gases with the metal wires and thus metal contamination from the hot wire source (metal filaments) and film impurities on the substrate surface, constant chamber cleaning, and constant breakdown and repair of the hot wire source. As uniformity of the thin films deposited on the surface of the substrate is controlled by the flows and the thermal decomposition reaction of the process gases, separation of the process gases prior to reaching the hot wires and/or prior to reaching processing zone above the surface of the substrate is needed.
Thus, the inventors believe that there is a need for a showerhead design of a HWCVD chamber which allows for excitation of a portion of the process gas mixture through hot wires in a low temperature HWCVD thin film deposition process in the absence of plasma and separated deliveries of various process gases without co-mingling of the gases prior to reaching the processing zone.